A “major, new narrative” on accurately quantifying methane emissions from livestock is largely supported by the science community – but largely “ignored” by mass media outlets, a US scientist contends.
Dr. Frank Mitloehner, a professor and air-quality specialist in the Department of Animal Science at the University of California, Davis, articulated this view whilst in conversation with Dr. Mark Lyons, president and CEO of Alltech, during last week’s virtual ONE20: The Alltech Ideas Conference.
He cautions that this scenario needs to be overcome in order to keep global agriculture on a “path to climate neutrality” – a concept that he says farmers can buy into, as supposed to the “current blame game”, which he says “does nothing other than antagonising agriculture versus the rest of society”.
The comments followed Dr. Mitloehner’s keynote presentation which, in fact, focused on this specific pathway for animal agriculture to become “climate neutral”.
To support his detailed argument, the expert in agricultural air quality, livestock housing and husbandry also drew upon scientific research from the University of Oxford where authors – Dr. Myles Allen and Dr. Michelle Caine – have found that biogenic methane from livestock “is not the same” as fossil methane from oil and gas.
“It is the same chemically, but the origin and fate is totally, drastically different,” Dr. Mitloeher said.
To explain this further, the professor focused on three main greenhouse gases: carbon dioxide (CO2); methane (CH4); and nitrous oxide (N2O), adding that these gases are “most often” compared to one another with respect to what’s called their “global warming potential” or GWP.
Global warming potential is a measure of how much heat a greenhouse gas traps in the atmosphere. Carbon dioxide equivalent is a measure used to compare the emissions from the various greenhouse gases based upon their global warming potential. In turn, this process makes it easier to sum up the emissions and contribution of greenhouse gases to climate change and determine options to address climate change, according to the Environmental Protection Agency (EPA).
In line with the EPA and the Intergovernmental Panel on Climate Change (IPCC) the global warming potentials of these three greenhouse gases are as follows:
- Carbon dioxide (CO2) GWP = 1;
- Methane (CH4) GWP = 28;
- Nitrous oxide (N2O) GWP = 265.
Dr. Mitloehner explains: “So, let’s say if you use 100lb of methane, then you multiply that 100lb of methane by 28 and then you have the CO2 equivalents.
“If you have 100lb of nitrous oxide emitted, then multiply that 100lb of nitrous oxide by 265 and you have the CO2 equivalents.
“That is what people have been doing since 1990 – since the Kyoto Protocol on climate was developed.”
Kyoto Protocol
The Kyoto Protocol is a historical agreement in that it was the first international agreement in which many of the world’s industrial nations concluded a verifiable agreement to reduce their emissions of six greenhouse gases in order to prevent global warming. The major feature of the Kyoto Protocol is that it set binding targets for 37 industrialised countries, and the European community, for reducing emissions. These amounted to an average of 5% against 1990 levels over the five-year period 2008-2012.
At the time, the scientists who were putting out this work on the global warming potential of these greenhouse gases had placed several caveats and footnotes underneath the tables in their reportage.
However, Dr. Mitloehner contends that, in much of the media coverage of this science, these important side notes and ‘explainers’ did not feature.
“The footnotes were cut off and people just ran with the main projections. In my opinion, that was a very dangerous situation that has really gotten animal agriculture into a lot of trouble quite frankly.
‘Short-lived pollutant’
“CO2 and N2O are referred to as ‘long-lived climate pollutants’. Methane, on the other hand, is a ‘short-lived climate pollutant’.
“Long-lived climate pollutants are only emitted, they are put into the atmosphere – but there is no real sink for it in a major way.
“But for methane, that is different,” he said.
Turning to what he calls the ‘global methane budget’, Dr. Mitloehner outlines the various sources of methane such as: fossil fuel production and use; agriculture and waste; biomass burning; wetlands; and other natural emissions.
Image source: Dr. Frank Mitloehner presentation at ONE20: The Alltech Ideas Conference
Globally, he says, a total of 560 teragrams (560 trillion grams) of methane is emitted into the atmosphere every year.
This, he says, is usually the point whereby the discussion stops – even though it shouldn’t.
“Because, in addition to emissions putting methane into the atmosphere, we also have sinks that amount to a very respectable total number of 550 teragrams (550 trillion grams).
These sinks are: the sink from chemical reactions in the atmosphere; and the sink in soils.
So, in other words, we have 560 teragrams of methane emitted, meaning put into the atmosphere, but then we have 550 teragrams of methane taken out of the atmosphere.
“Therefore, the net emissions that we are dealing with per year is not 560 teragrams – but it is actually 10 teragrams. Yet, everybody talks about 560 teragrams.
‘Hydroxyl oxidation’
“So what is it that takes methane out of the atmosphere? What is that process?
“Well, it’s called ‘a chemical reaction’ in the atmosphere; the scientific term is ‘hydroxyl oxidation’. Hydroxyl oxidation is a process by which radicals in the air take hydrogen away from methane (CH4), it destroys the methane converting it back to CO2 again,” he said.
In addition to this difference between the greenhouse gases – namely their global warming potential – another difference is the lifespan of these gases.
“Carbon dioxide has a lifespan of 1,000 years – once it’s in the atmosphere it lives there for 1,000 years.
“It’s similar for nitrous oxide – not quite as long, buts it’s in the hundreds of years (circa 120 years). So both carbon dioxide and nitrous oxide are considered ‘long-lived’ climate pollutants.
And they have a sharp contrast to methane, as methane has a half-life of 10 years – meaning that the methane that our cows and our livestock put out will be gone after 10 years.
“Methane is not just produced – methane is also destroyed,” he said.
Again, Dr. Mitloehner warns that this is a very important nuance most often not considered in much coverage on the topic.
Recycled Methane
Turning to the biogenic carbon cycle, the professor says it is critical to understand where the carbon – the ‘C’ in CH4 (methane) – comes from, and where that carbon ends up.
“The origin and the fate of that carbon is actually very important in order to understand why livestock-related greenhouse gases are distinctively different from greenhouse gases that are associated with other sectors of society – such as the transportation sector or other fossil-fuel-using sectors.
“So, what do plants need to grow? They need sunlight, they need water and they need carbon in the form of CO2.
“That CO2 in the atmosphere is taken in by plants; that carbon from CO2 is then made into carbohydrates – such as cellulose [found in grass or plants] and that cellulose starch, or component in the feed, is then ingested by, let’s say, a cow.
“So the C goes from atmospheric CO2, to carbohydrates in the plant, into the ruminant’s stomach, into the rumen, where some of that carbon is converted into methane (CH4) and emitted – they belch it out.
Image source: Dr. Frank Mitloehner presentation at ONE20: The Alltech Ideas Conference
“After about a decade, that CH4 is converted – via hydroxyl oxidation – back into CO2. So, in other words, the origin and the fate is atmospheric CO2 – what we are dealing with here is a cycle – the biogenic carbon cycle.
“Therefore, if you have constant livestock herds, or even decreasing livestock herds over time, then you’re not adding new additional carbon to the atmosphere. But the carbon that is emitted by our animals is recycled carbon,” Dr. Mitloehner said.
However, he stresses that he is “by no means” suggesting that methane does not matter.
While that methane is in the atmosphere, he affirms that it is heat-trapping and that it is a potent greenhouse gas.
Rather he says, the question really is, do livestock herds add to additional methane – meaning additional carbon in the atmosphere – leading to additional warming?
“The answer to that question is no. As long as we have constant herds, or even decreasing herds, we are not adding additional methane – and hence not additional warming.
“This is a total change in the narrative around livestock. And I think this will be the narrative in the years to come,” he said.
Image source: Dr. Frank Mitloehner presentation at ONE20: The Alltech Ideas Conference
In contrast, he outlines how fossil carbon originates in the form of fossil fuels – oil, coal, gas – which are nothing more than ancient forests and animals that died and fossilised over hundreds of millions of years – and got stored in the ground.
‘One-way street’
Now global industries are extracting them – from land and sea – for oil, gas etc and, sooner or later, burning that fossil fuel in factories, in cars, in trucks, in trains, planes and ships,
“We take carbon out of the atmosphere where it was trapped. We are extracting it, we are burning it, and by doing so we are putting it into the atmosphere. And this is not a cycle; but this is a one-way street.
“And because the amount of CO2 that we put into the atmosphere – by far – overpowers the potential sinks that could take up CO2 – such as oceans, soils, or plants – this, ladies and gentlemen, is the main culprit of greenhouse gases in our atmosphere and the resulting warming.
Image source: Dr. Frank Mitloehner presentation at ONE20: The Alltech Ideas Conference
Dr. Mitloehner outlined that long-lived climate pollutants (such as carbon dioxide and nitrous oxide) are referred to as “a stock gas” because every time its emitted into the atmosphere – for example, when driving a car – it adds to the existing stock of that gas.
By contrast, he says that methane is referred to as “a flow gas” whereby you have constant amounts being emitted from constant sources – for example, a constant number of cows on a dairy farm. In this scenario, he again reiterates that new additional methane is not being added to the atmosphere because the amount of methane the cows put out “equals the amount” of methane that’s being destroyed.
“I have yet to see a climate scientist who would say that ‘it’s the cows that are a primary culprit of warming’. Most of them will agree that the primary culprit is the use of fossil fuels.
“However, people critical of animal agriculture always point at cows and cattle and other livestock species. And they feel that this is a very powerful tool to ostracise animal agriculture as we know it,” he said.
As far as the science is concerned, Dr. Mitloehner says the only time that you really add new additional methane to the atmosphere with a livestock herd is throughout the first 10 years of its existence; or if you increase your herd sizes – only then, he says, do you actually add new additional methane and thus new additional warming.
‘Global cooling’
So what does all this mean in reality? How does the way countries currently account for greenhouse gases differ to how they should account for greenhouse gases, particularly methane?
While significant increases in methane will lead to increased warming, he says stable methane levels will have “a zero impact” on warming, as the amount of methane produced and the amount of methane destroyed “even each other out”.
For Dr. Mitloehner, the most exciting outlook for this science is that, where methane is significantly decreased, it means carbon can actively be taken out of the atmosphere.
Image source: Dr. Frank Mitloehner presentation at ONE20: The Alltech Ideas Conference
“This scenario has a net cooling effect. If you have a methane reduction it leads to a significant cooling, meaning that, if we can find ways to reduce methane, then we counteract other sectors of societies that do contribute – and significantly so – to global warming, such as flying, driving, running air conditioners and so on. “So if we were to reduce methane, we could induce global cooling. And I think that our livestock sector has the potential to do it – and we’re already seeing examples where that happens,” he said.
Dr. Mitloehner went on to refer to the methane emission reduction levels being achieved in the US state of California – the largest agricultural state in the US – where the farming sector has achieved a staggering 25% reduction in its emission rates due to state-incentivised support for anaerobic digestion in the dairy sector and alternative manure management practices.
The state is aiming for a 40% reduction of methane emissions by 2030.
“We are now at 25% of the 40% total reduction – so over halfway of where we want to be; so to me that is very encouraging and I’m really happy to report that – because I know that if we can do it here, it can be done in other parts of the country – and in other parts of the world.
“And if we indeed achieve such reductions of greenhouse gas, particularly of short-lived greenhouse gases such as methane, then that means that our livestock sector will be on a path for climate neutrality – and that to me is a lifetime objective,” he said.
Image source: Dairy Cares
The professor also pointed to strides being achieved in New Zealand where legislation has been developed that separates out biogenic methane from other greenhouse gases.
The government there now has regulations for carbon dioxide and nitrous oxide – the long-lived climate pollutants – and different goals and different policies around biogenic methane.
Media silence
Dr. Mitloehner, who received his master’s degree in animal science and agricultural engineering from Leipzig University in Germany and his PhD in animal science from Texas Tech University, brought this concept of ‘global warming potential star’ (GWP*) to the Food and Agriculture Organisation of the United Nations (FAO) when he served as chairman of an international partnership committee called ‘LEAP’ (Livestock Environmental Assessment and Performance Partnership).
“They are greatly interested in this concept of accounting for methane for its warming potential – as opposed to just the CO2 equivalent calculation.
“The concept has also made it all the way to the Intergovernmental Panel of Climate Change – where one of its senior authors is Dr. Myles Allen from Oxford University who is the one behind this concept.
But now, what I find most interesting is that the one missing entity in this whole discussion so far has been the media.
“I have not seen any major reporting on this – even though it’s such a hot topic.
“I mean the world talks about what the impact of our food systems are on our environmental footprint.
“Now, this is a major new narrative, and to me it’s very unusual, and it’s very confusing, as to why the same outlets that have touted this topic as being ‘so paramount’ are not talking about these new findings whatsoever.
To me, that’s problematic. And we have to think about why that is? Have we not explained it right? Is it too early for them to report about it? I don’t know, but this narrative is not going away.
“You will see it gain momentum and it will become the new reality,” he concluded.
